A new solute clearance procedure will be used to detect alterations in the permeability of the distal air-blood barrier in patients with adult respiratory distress syndrome, cardiogenic pulmonary edema and chronic interstitial lung disease. Subjects inhale an aerosol containing either 99mTe-diethylenetriamine penteacetate or 99mTc04- and regional clearance is measured with a computerized gamma camera. Abnormally rapid clearance has been documented in a variety of forms of interstitial disease which are associated with alveolar epithelial abnormalities. A distinction between pulmonary edema due to alveolar wall damage and increased hydrostatic pressure will be sought with this technique. The isolated rabbit lung preparation will be studied with steady-state indicator dilution procedures to obtain measurements of the vascular, extracellular and cellular compartments of the lung. The effect of airway pressure, pharmacologic agents, vasoactive and toxic substances on these volumes will be assessed. In addition, studies of inhaled solute clearance, capillary reflection coefficients, and permeability to extracellular solutes and HCO3- will be conducted in this preparation.